We request funds to purchase a Becton Dickinson custom multilaser LSRII flow cytometer for polychromatic analytical flow cytometry. The current facilities at Vanderbilt University provide a strong infrastructure for conduct of highly technical flow cytometric work, but do not currently meet the scientific needs for the NIH-funded community of scientists. First, many of the scientists in the user group have expanded their use of new fluorophores, quantum dots, and variant GFP molecules in an effort to intensify the polychromatic nature of the work, which is needed for complex functional readouts. Many of these investigators are using these novel combinations of fluorophores in microscopy, but now need the more quantitative analysis that is afforded by flow cyto- metry. The currently available instruments are lacking lasers in critical regions of the spectrum for the conduct of these studies. In addition, researchers are becoming limited in access to analytical instruments because the amount of use of the current instruments exceeds 45 hours per week per instrument, not counting the time needed for daily setup and calibration. Limitation of access has begun to constrain the progress of our NIH-funded researchers. This instrument will support a highly collaborative group of 19 major users from 9 research groups in the School of Medicine. Ongoing, NIH-funded projects by major users that will benefit include research on vaccine responses, cancer, autoimmunse diseases, development, basic immune responses and others. For each project, the requested instrumentation will have an immediate and substantial impact by providing unique new analytical capabilities of the cells under study, and increased access to analytical cytometry. Acquisition and operation of this cytometer by the Vanderbilt Flow Cytometry Core Laboratory, an institutional shared resource, will guarantee user training/support, 24 hour/day 7 day/week access, and instrument maintenance and repair. User fees will cover staff support, service and repair. The institution has made an exceptionally strong financial commitment to support maintenance and use of the instrument. Other researchers will be able to use available time, as the instrument will be sited in an institutional core, thus maximizing use and impact. This Core currently supports over 200 users who we have trained in analytical and sorting cytometry at Vanderbilt. PUBLIC HEALTH RELEVANCE: The proposed state-of-the-art instrument will give researchers a new capability and expanded access to study important functions of cells including the immune system, stem cells, and cell leading to cancer, thereby improving our ability to develop new targets for intervention in human diseases.